1. Field of the Invention
The present invention relates to an exhaust silencing device having inner tubes which are connected to an exhaust pipe and provided with a plurality of through holes, and an outer tube covering the inner tubes.
2. Description of Background Art
An exhaust silencing device has been known, for example, as set forth in Japanese Utility Model (Kokoku) Publication Nos. Hei 5-5213 and Hei 5-5220. According to the exhaust silencing device disclosed in the Japanese Utility Model (Kokoku) Publication No. Hei 5-5213, a sound absorbing material such as glass wool is filled in between the inner tubes and the outer tube for the purpose of deadening an exhaust sound by the sound absorbing function of the sound absorbing material. However, this type of construction for holding the sound absorbing material becomes complicated and results in an increase in the cost.
In Japanese Utility Model (Kokoku) Publication No. Hei 5-5220, no sound absorbing material is filled in a space between the inner tubes and the outer tube. The space is used as an expansion chamber, whereby a shortcoming of the use of the sound absorbing material is obviated. However, production of a high-frequency component sound, a so-called whistling sound, cannot be prevented.